Friday, December 1, 2023

Frosty moon and star trails

 The recent full moon of 27 November, the 11th of the year, has traditional nicknames that differ depending on the source, but the one that seems appropriate this year is "Frost Moon".  According to The Old Farmer's Almanac this name comes from the Cree and Assiniboine cultures.  In the popular press it has been more commonly hyped as the "Beaver Moon", which is the prevailing nickname.  

Full moons with snow on the ground present interesting photographic opportunities.

Olympus E-M1iii + Leica 9mm f/1.7, live composite mode, 1 hour.

 When I retrieved the camera after this exposure the lens was frosting over and the battery was dead.  The outside temperature was 5° F, dropping toward an eventual low of -12° F the next morning.  Frosty indeed.

The Frost Moon.  AT80EDT telescope.

The Beaver Moon setting over Bristol Head


The setting-moon pictures were taken on the morning of the 28th. The temperature was -11° F at the time.  It kept dropping.

Sunday, November 19, 2023

Some old telescopes brought back to life

 A neighbor recently brought over a large box of telescope parts, hoping that I could help make sense of what he had.  After some sorting, puzzling, and discarding of useless parts, it turned out that there were three potentially useful telescopes.  It took only a modest investment in new parts to create a working alt-azimuth mount.  I was also able to contribute some other accessories that have been sitting unused in my closet for many years.

The three scopes, which are now all in operating condition with interchangeable accessories, are:

  1.  Celestron C90 f/11 (1000 mm focal length)
  2.  Tasco 60mm f/15 (900 mm focal length)
  3.  Celestron Firstscope 60Az f/12 (700m focal length)

The focal ratios are rounded to the nearest integer.  The stated focal lengths are the numbers printed on the scopes.  The C90 is a Gregory-Maksutov design with the old classical helical-focusing barrel. Based on the date printed on the manual (10/98) it is probably from the late 90s or early 00s.  The the 60mm scopes are air-spaced achromats of unknown age.

Last night the sky cleared unexpectedly after a snowy and rainy day.  I took two of the scopes out to test them on the Moon and Saturn.

Here is the Celestron Firstscope:

The mount consists of a Neewer 36mm low-profile ball head, a PrimaLuceLab 140mm PLUS dovetail plate, and two JJC TR-1II tripod mount rings supplemented with felt.  The dovetail plate is dual-sided: one side has an Arca-Swiss dovetail groove and the other side is a Vixen dovetail.  That makes it compatible with photo mounts or telescope mounts, depending on which side is facing out.  The tripod mount rings are made for Canon telephoto lenses but work quite well with this tube diameter (63mm) when padded out with felt strips.  

This mount configuration works much better than whatever came with the telescope originally.  It is possible to rotate and slide the tube for optimal balance and accessory position, and the long dovetail gives additional balance adjustment as well as being compatible with most standard photo and telescope mounts.  In the above photo both the dovetail plate and optical tube are pushed well forward of normal to balance the weight of the camera.

Here is a picture of the 5.8-day-old moon taken with this setup:

C60 + E-M5iii, ISO 800, 1/50 s.  Untracked.

These "beginner" telescopes can perform quite well when used with proper mounts and accessories.  The moon diameter in this image corresponds to a focal length of 704mm, very close to the number printed on the scope.  The actual focal ratio is then 704/60 = 11.7.

The C90 started out on the same ball-head mount:

 After a few exposures I decided to switch to a computer-driven mount and astro camera in order to get higher resolution.

Here the C90 is riding on an iOptron SmartEQ Pro+ computerized mount with a ZWO ASI178MC camera.  The iPad tablet controls the mount via wifi and the laptop computer is running the camera over a USB cable connection.

I took short videos of the Moon and then switched over to Saturn.  The files were processed with AutoStakkert and Registax. 

Looks like a great scope!

The measured diameter of the moon in the above shot with the C90 yields a focal length of 791 mm.   The focal length of moving-mirror scopes (like this one) will change to match the exact position of the focal plane (image sensor location), so this difference between the measured and labeled focal lengths might be completely normal.

I didn't night test the Tasco scope, but I did use it to snap a few daytime pics of the local mountains.

Bristol Head

Any photo taken at this distance with this focal length (900 mm) will be affected by atmospheric blurring and this one is no exception.  However, it performed quite well in spite of the turbulence.

Tasco 60mm f/15 on a Stellarvue M002C alt-az mount.

The Tasco scope in this photo is using the same rings and dovetail bar as the Celestron 60mm, but the dovetail bar has been flipped over so that it will fit into the Vixen slot in the Stellarvue mount.

added 11/20:

It is 24° F with snow on the ground, but the sky is clear so I set up the Tasco on the porch and took a quick shot of the 8.1-d old moon:

Tasco 60mm f/15 + E-M5iii.  ISO 400, 1/160 s. Untracked.

The moon diameter in this image yields a calculated focal length of 909 mm, within 1% of the number printed on the scope.

As usual, click an image to get into gallery view, then download or open in a new tab to see the full-size images.

Thursday, November 16, 2023

The Flying Star

 The star 61 Cygni in the constellation Cygnus (The Swan) has the largest proper motion of any naked eye star at 5.3"/yr, about half that of Barnard's Star.  The motion was first noted by Giuseppe Piazzi  in 1804 (three years after he discovered Ceres) and the star acquired the nickname "Piazzi's Flying Star".  It's distance was measured via parallax by Friedrich Bessel in 1836.  Bessel's result was the first direct distance measurement for any star other than our sun. At 11.4 ly it is the 14th closest star system and the 5th closest naked-eye star, after Procyon. 

61 Cygni is actually a double-star system with the two stars having a combined magnitude of 4.8.  Separated by about 31" they are an easy target for small telescopes.  Under fairly dark sqml=21.4 skies I was just barely able to make out this star with averted vision after a few minutes of letting my eyes adjust, so the "naked eye" designation is definitely a personal attribute.  It was dead easy with a 2x54 binocular.

Cygnus setting over Bristol Head. 61 Cyni is marked by the white circle. EM1iii + Leica 15mm f/1.7 + softon. ISO 1600, 60 s.

E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.

61 Cygni. E-M5iii + AT60mmED f/6 refractor. ISO 1600, 10 s. 0.5° field.

Imaging the Gas Giants

 The Gas Giant planets are Jupiter, Saturn, Uranus, and Neptune.  I recently decided to take a try at capturing images of Jupiter and Saturn.  How hard could it be?  Pretty hard, it turns out.

The problem with high-resolution imaging is that air currents are constantly shifting the image of the object under study.  When we view an object through an eyepiece our brain tends to filter out the small movements and we learn to perceive detail in spite of the motion.  A camera is not so forgiving.  A single exposure captures the image at one moment in time when things might be in rapid motion and therefore blurred.  The solution is to record video and then select the sharpest frames and add them together to get an integrated picture using only the best data obtained.  So that is what I did, after watching many online videos to benefit from the experience of others.

For these images I used a Celestron C8 SCT (Schmidt-Cassegrain Telescope).  The video camera was a ZWO ASI178MC astro camera, which has 0.0024 mm pixels.  With this pixel size and the 2032 mm (approximate) focal length of the telescope, the image scale was 0.24 arcsec per pixel.  An 8" scope has a resolution of about 0.6 arcsec, so this is probably an adequate amount of oversampling.

The video clips (each less than one minute long) were processed with a program called AutoStakkert.  The sorted and stacked images were then further processed with a program called RegiStax.  The results are shown below.

Saturn, 04 Nov 2023.  Celestron C8 + ASI178MC.

Jupiter, 04 Nov 2023.  Celestron C8 + ASI178MC.

As a first try (ignoring earlier non-video attempts) I am pleased with the results.  However, these images are not so great on an absolute scale.  On a quality scale of 1-10, where "1" represents a blurry image from a cellphone hand-held up to the eyepiece, and "10" represents Hubble-esque images from 11-14" scopes produced by skilled practitioners, these rank at about a "3" (maybe 4, but definitely no higher).  There is much room for improvement.  Will I continue?  I don't know - these kind of images require a lot of computer processing and storage and are really a lot of work.  I think I would rather spend my time fishing, biking, or skiing rather than sitting in front of a computer monitor.

As a counterpoint, I also captured a wide-angle image of Uranus which was a single 60 sec exposure at an image scale too large to see the planet's disc.  This one-and-done type of imaging is more to my liking.

Uranus, 04 Nov 23.  E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.

Past and Future Supernovas

The red supergiant star Betelgeuse is a well-known and prominent feature of the constellation Orion (The Hunter), forming the right shoulder of the imaginary hunter.  Betelgeuse is about 18 times the mass of our sun and is only 10 million years old.  Stars this massive burn rapidly, however, so Betelgeuse is actually nearing the end of its lifetime.  When its nuclear fuel is exhausted the outer layers will collapse and then rebound in an immense explosion as a supernova.  Predicting when this collapse will occur is very tricky, but current estimates range from tens to thousands of years. 

In the constellation Taurus, about midway between Orion and Auriga, lies the remnant of a previous supernova that occurred less than a thousand years ago, in 1054 AD.  This remnant is known as the Crab Nebula.  It was discovered by the English astronomer John Bevis in 1731. It was subsequently observed in 1758 by the French comet hunter Charles Messier, who was searching for the predicted return of Halley's comet.  When Messier realized that the object was not moving it inspired him to begin his catalog of comet-like objects now known as the Messier Catalog.  The Crab Nebula (the name it acquired in the 1840s) is the first object in the catalog: M1.

Betelgeuse is the orange star in the middle of the frame.  The position of the Crab Nebula is marked with a white circle.  Sony A7iii + Laowa 15mm f/2  + softon filter.

When viewed in a small telescope M1 is an indistinct fuzzy blob.

M1, The Crab Nebula.  The bright star lower left is magnitude-3 Zeta Tauri.  E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.

 The supernova that produced the Crab Nebula was recorded unambiguously by Chinese astronomers of that time, but there is also a pictograph on a cliff overhang in Chaco Canyon, NM that is theorized to be a depiction of the event.

Chaco Canyon, NM, 1987.

Wednesday, November 15, 2023

The River and the Whale

 The neighboring constellations Eridanus (The River) and Cetus (The Whale) cross the southern meridian during late night in mid-October.  Between the two of them they contain four of the nearest star systems and two of the nearest naked-eye stars: magnitude-3.7 Epsilon Eridani (Ran) and magnitude-3.5 Tau Ceti.  These two stars are circled in the image below, Epsilon Eridani on the left, Tau Ceti on the right.

E-M1iii + Leica 15mm f/1.7 + softon filter.

Epsilon Eridani, aka "Ran",  is 10.5 ly distant, the third closest naked-eye star (after Alpha Centauri and Sirius), and the 9th closest star system overall.  Tau Ceti is 11.9 ly distant and is the 9th closest naked-eye star and the 19th closest star system.  

Epsilon Eridani has one known planet and two asteroid belts. Tau Ceti has two confirmed planets and possibly an additional six that are suspected.  Both of these stars are slightly smaller than our sun at about 80% of the sun's mass.

The finder chart below shows both naked-eye stars and two nearby red-dwarf stars: UV Ceti and YZ Ceti, which are the 6th and 21st closest star systems, respectively. These two stars are too faint to show up in the image above, but were discussed in a previous post here.



Friday, November 10, 2023

Open Clusters in Auriga

 The constellation Auriga contains three open clusters cataloged by Charles Messier: M36, M37, and M38.  

Auriga and star clusters

M36.  E-P5 + Rokinon 135mm f/2. ISO 1600, 60 s.

M37.  E-P5 + Rokinon 135mm f/2. ISO 1600, 60 s.

M38 + NGC 1907 (below).  E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s.

All of these clusters are 4000+ light years distant.  The region including M36 and M38 is shown here in a 4° view: